U.S. patent number 4,953,677 [Application Number 07/330,221] was granted by the patent office on 1990-09-04 for method of and apparatus for controlling direct coupling mechanism in hydrodynamic driving apparatus.
This patent grant is currently assigned to Honda Giken Kogyo Kabushiki Kaisha. Invention is credited to Takashi Aoki, Yoshihisa Iwaki, Kimihiko Kikuchi, Hiroshi Nakayama, Hiroyuki Shimada, Satoshi Terayama.
United States Patent |
4,953,677 |
Aoki , et al. |
September 4, 1990 |
Method of and apparatus for controlling direct coupling mechanism
in hydrodynamic driving apparatus
Abstract
The amount of engagement of a direct couping mechanism such as
lockup clutch (6) disposed between input and output members of a
hydrodynamic driving apparatus such as a torque converter (5) to
mechanically connect or disconnect the input and output members
(5a, 5b) is controlled so as to bring a parameter indicative of the
amount of slippage between the input and output members into a
predetermined reference range. The average value of the parameter
which is measured in a prescribed time interval is determined, and
a control value for the amount of engagement in a next prescribed
time interval is determined based on the differnece between the
average value and the predetermined reference range value.
Inventors: |
Aoki; Takashi (Saitama,
JP), Terayama; Satoshi (Tokyo, JP), Iwaki;
Yoshihisa (Saitama, JP), Shimada; Hiroyuki
(Saitama, JP), Kikuchi; Kimihiko (Tokyo,
JP), Nakayama; Hiroshi (Saitama, JP) |
Assignee: |
Honda Giken Kogyo Kabushiki
Kaisha (Tokyo, JP)
|
Family
ID: |
26418559 |
Appl.
No.: |
07/330,221 |
Filed: |
March 29, 1989 |
Foreign Application Priority Data
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Mar 30, 1988 [JP] |
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63-77488 |
Mar 30, 1988 [JP] |
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63-77489 |
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Current U.S.
Class: |
192/3.3;
192/3.31 |
Current CPC
Class: |
F16H
61/143 (20130101) |
Current International
Class: |
F16H
61/14 (20060101); F16H 045/02 () |
Field of
Search: |
;192/3.29,3.3,3.31 |
References Cited
[Referenced By]
U.S. Patent Documents
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|
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4579208 |
April 1986 |
Nishikawa et al. |
4618037 |
October 1986 |
Nishikawa et al. |
4660697 |
April 1987 |
Yoneda et al. |
4700819 |
October 1987 |
Nishikawa et al. |
|
Foreign Patent Documents
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0049160 |
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Mar 1985 |
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JP |
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0143266 |
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Jul 1985 |
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JP |
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61-286665 |
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Dec 1986 |
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JP |
|
Other References
1 page doucument (22 M 590); English summary of 61-286665 Japanese
patent publication..
|
Primary Examiner: Bonck; Rodney H.
Attorney, Agent or Firm: Lyon & Lyon
Claims
What is claimed is:
1. A method of controlling a direct coupling mechanism disposed
between input and output members of a hydrodynamic driving
apparatus to mechanically connect or disconnect the input and
output members, wherein engagement of the direct coupling mechanism
is controlled so that a parameter indicative of slippage between
said input and output members falls in a predetermined fixed
reference range, said method comprising the steps of:
determining an average value of said parameter which is measured in
a prescribed time interval; determining a control value for said
engagement in a next prescribed time interval based on a difference
between said average value and said predetermined reference range
value; and controlling engagement of said direct coupling mechanism
based on said control value in said next time interval.
2. A method according to claim 1, wherein the area of a map
determined based on the output power of an engine coupled to said
input member and the speed of said output member is divided into an
off range, a feedback range, a control range, a semitight range,
and a tight range, said method further including the step of:
controlling said amount of engagement to keep said parameter in
said predetermined reference range when a driving condition
determined by said output power of the engine and said speed of the
output member is in said feedback range.
3. A method of controlling a direct coupling mechanism disposed
between input and output members of a hydrodynamic driving
apparatus to mechanically connect or disconnect the input and
output members, so that the amount of engagement of the direct
coupling mechanism is controlled so as to bring a parameter
indicative of the amount of slippage between said input and output
members into a predetermined reference range, said method
comprising the steps of:
determining the average value of said parameter which is measured
in a prescribed time interval;
determining a control value for said amount of engagement in a next
prescribed time interval based on the difference between said
average value and said predetermined reference range value;
wherein the area of a map determined based on the output power of
an engine coupled to said input member and the speed of said output
member is divided into an off range, a feedback range, a control
range, a semitight range, and a tight range;
controlling said amount of engagement to keep said parameter in
said predetermined reference range when a driving condition
determined by said output power of the engine and said speed of the
output member is in said feedback range;
storing as a learned value a control value employed in correcting
said amount of engagement when said driving condition is in said
feedback range; and
controlling said amount of engagement by employing said stored
latest learned value when said driving condition is in said control
range or said semitight range.
4. A method according to any one of claims 1 through 3, wherein
said hydrodynamic driving apparatus comprises a torque converter
having an impeller as said input member and a turbine as said
output member, and said direct coupling mechanism comprises a
lockup clutch for selectively connecting and disconnecting said
impeller and said turbine.
5. A method according to claim 4, wherein a speed ratio "e" of said
impeller to said turbine represents said parameter.
6. A method according to claim 5, wherein said predetermined fixed
reference range corresponds to a range of said speed ratio between
a lower speed ratio limit "e.sub.L " and an upper speed ratio limit
"e.sub.H ".
7. A method according to claim 6, wherein said lower speed ratio
limit "e.sub.L " is 0.95 and said upper speed ratio limit "e.sub.H
" is 0.98.
8. An apparatus for controlling a direct coupling mechanism
disposed between input and output members of a hydrodynamic driving
apparatus to mechanically connect or disconnect the input and
output members, and said apparatus comprising:
a shift valve for selectively engaging and disengaging said direct
coupling mechanism;
a control valve for controlling the amount of engagement of said
direct coupling mechanism;
a timing valve for keeping said direct coupling mechanism in a
fully engaged condition;
a first solenoid valve which can be selectively turned on and
off;
a second solenoid valve which can be controlled in duty ratio;
said shift valve, said control valve, and said timing valve being
controllable in operation solely by a constant oil pressure
supplied dependent on the turning on and off of said first solenoid
valve and a duty-ratio-controlled oil pressure supplied dependent
on the duty ratio control of said second solenoid valve;
said direct coupling mechanism being operable selectively into a
disengaged condition by supplying an oil pressure to a release
passage thereof, a partly engaged condition by supplying a control
oil pressure corresponding to said duty-ratio-controlled oil
pressure to said release passage, and a fully engaged condition by
cutting off the supply of the oil pressure to said release
passage.
9. An apparatus according to claim 8, wherein the area of a map
determined based on the output power of an engine coupled to said
input member and the speed of said output member is divided into an
off range, a feedback range, a control range, semitight range, and
tight range, said direct coupling mechanism being operable into
said disengaged condition when a driving condition determined by
said output power of the engine and said speed of the output member
is in said off range, into said partly engaged condition when said
driving condition is in said feedback range, said control range, or
said semitight range, and into said fully engaged condition when
said driving condition is in said tight range.
10. An apparatus according to claim 8 or 9, wherein said
hydrodynamic driving apparatus comprises a torque converter having
an impeller as said input member and a turbine as said output
member, and said direct coupling mechanism comprises a lockup
clutch for selectively connecting and disconnecting said impeller
and said turbine.
11. A method of controlling the amount of engagement of a direct
coupling mechanism disposed between input and output members of a
hydrodynamic driving apparatus in a motor vehicle to mechanically
connect and disconnect the input and output members, said method
comprising the steps of:
establishing, depending on a driving condition of the motor
vehicle, an off range in which the direct coupling mechanism is
disengaged, a feedback range in which said amount of engagement is
controlled under feedback control to keep a parameter indicating
the amount of slippage between the input and output members within
a predetermined reference range, a semitight range in which said
amount of engagement is controlled to engage the direct coupling
mechanism while the motor vehicle is running normally and to cause
the direct coupling mechanism to slip while the motor vehicle is
being accelerated, and an on range in which the direct coupling
mechanism is fully engaged; and
determining a control value for the amount of engagement of the
direct coupling mechanism in said semitight range based on a
control value for the amount of engagement when said parameter is
kept within said predetermined reference range in said feedback
range.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a method of and an apparatus for
controlling a direct coupling mechanism such as a lockup clutch or
the like to mechanically connect and disconnect the input and
output members of a hydrodynamic driving apparatus such as a torque
converter or the like.
Conventional automatic transmissions for use in automobiles are
generally in the form of a combination of a hydrodynamic driving
apparatus such as a torque converter, for example, and a
transmission gear shifting mechanism. The hydrodynamic driving
apparatus suffers slippage during the transmission of engine power
since the engine power is transmitted through a fluid in the
hydrodynamic driving apparatus. The slippage thus caused results in
poor fuel economy and an increase in the engine rotational speed
which in turn produces greater engine sounds.
To avoid the above drawbacks, some transmissions employing such a
hydrodynamic driving apparatus includes a direct coupling mechanism
such as a lockup clutch, for example, for directly mechanically
connecting the input and output members of the hydrodynamic driving
apparatus (e.g. the impeller and turbine of a torque converter).
The engine power is transmitted through the torque converter only
while the automobile is running in a low speed range, or when gear
shifts are effected, and the lockup clutch is engaged for improved
fuel economy and reduced engine sounds in other occasions.
The lockup clutch may be controlled such that it is simply engaged
or disengaged, or it is selectively engaged, partly engaged, and
disengaged. The latter control is effected in a certain driving
mode in low- and medium-speed ranges. According to this control
process, the torque converter is not completely directly connected,
but the lockup clutch or direct coupling mechanism is controlled to
cause slippage when the torque varies at a peak value. For example,
the ratio e of the rotational speeds of the input and output
members of the torque converter, or a slip ratio (1-e), is
calculated, and fed back for controlling the direct coupling
mechanism so that the speed ratio e will not become 1 or the slip
ratio will not become 0 in the aforesaid certain driving mode. Such
a control method is disclosed in Japanese Laid-Open Patent
Publication No. 61-286665, for example.
With the lockup clutch being thus variably engageable under the
feedback control, however, a system for controlling the amount of
engagement of the lockup clutch is inevitably subject to a certain
delay in operation. In addition, the control process is adversely
affected by the detecting errors of sensors which detect the
rotational speeds of the input and output members of the torque
converter or an error produced in calculating the speed ratio or
slip ratio. For these reasons, the amount of engagement of the
lockup clutch may be excessively or insufficiently corrected, and
hence the lockup clutch may not stably controlled, with the results
that the rotational speed of the input or output member of the
torque converter tends to surge or vary.
In order to solve the above problems caused by the error in
detecting the rotational speeds or the error in calculating the
speed ratio or the slip ratio, the applicant has proposed a control
method by which a control value for the amount of engagement of a
lockup clutch is maintained at a constant level for a predetermined
period of time, and a control value for a next period of time is
determined based on the ratio e of the rotational speeds of the
input and output members of a torque converter at the end of the
predetermined period of time.
According to the proposed control method, the amount of engagement
of the lockup clutch can be stably controlled to suppress any
surging or variation of the rotational speed of the output member
of the torque converter. If the control method is carried out while
the automobile is being accelerated, for example, the speed ratio e
increases even when a control value for the amount of engagement of
the lockup clutch is constant. Therefore, where the speed ratio e
is detected at the end of a predetermined period of time and a
control value for a next period of time is determined based on the
detected speed ratio e on a real-time basis, the amount of clutch
engagement is overly corrected, lowering the engine rotational
speed. As a result, the automobile runs in an embarrassing
situation in which it is accelerated while the engine rotational
speed is being lowered.
The direct coupling mechanism or lockup clutch is controlled by
employing two control hydraulic pressures, i.e., a modulated
pressure supplied by turning on and off two solenoid valves, and a
throttle pressure commensurate with the opening of the throttle
valve of the engine. These control hydraulic pressures are used to
control the operation of a lockup shift valve, a lockup control
valve, and a lockup timing valve for engaging and disengaging the
lockup clutch. The throttle pressures is also employed to control
hydraulic clutches for effecting gear shifts. Since the throttle
hydraulic pressure fluctuates when a gear shift is made, therefore,
the control of the lockup clutch is liable to become unstable.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method of
controlling a direct coupling mechanism to prevent an automobile
from running in an embarrassing fashion, to stably control the
amount of engagement of the direct coupling mechanism, and to
suppress surging or variations of the rotational speed of the
output member of a torque converter.
Another object of the present invention is to provide an apparatus
for effectively controlling the foregoing direct coupling
mechanism.
Still another object of the present invention is to provide an
apparatus for controlling the amount of engagement of a direct
coupling mechanism without employing a throttle pressure as a
control hydraulic pressure.
According to a control method of the present invention, the amount
of engagement of a direct coupling mechanism disposed between input
and output members of a hydrodynamic driving apparatus to
mechanically connect and disconnect the input and output members is
controlled so as to bring a parameter indicative of the amount of
slippage between the input and output members into a predetermined
reference range. The average of values of the parameter which are
measured in a prescribed time interval is determined, and a control
value for the amount of engagement in a next prescribed time
interval is determined based on the difference between the average
and the predetermined reference range.
With the control method of the invention, the control value for the
amount of engagement of the direct coupling mechanism is
established dependent on the difference between the previous
average of the values of the parameter and the predetermined
reference range, and the established control value is kept as it is
in the present time interval. Since the control value remains at a
constant level during the prescribed time interval, the rotational
speeds of the input and output members of a torque converter are
prevented from being surged or varied. As feedback control is
effected based on the average of the parameters in the prescribed
time interval, the automobile is prevented from running in an
embarrassing situation in which it would be accelerated while the
engine rotational speed is being lowered.
The control apparatus of the present invention employs, as control
oil pressures, the constant oil pressure supplied dependent on the
turning on and off of the first solenoid valve and the
duty-ratio-controlled oil pressure supplied dependent on the duty
ratio control of the second solenoid valve, for controlling the
operation of the lockup shift valve, the lockup control valve, and
the lockup timing valve. The lockup clutch is operable selectively
into a disengaged condition in which the lockup clutch is
disengaged by supplying a prescribed oil pressure to a release
passage thereof, a lockup control condition in which the lockup
clutch is partly engaged by supplying the release passage with a
control oil pressure lower than the prescribed oil pressure and
corresponding to the duty-ratio-controlled oil pressure, and an
engaged condition in which the lockup clutch is fully engaged by
cutting off the supply of the oil pressure to the release
passage.
Further scope of applicability of the present invention will become
apparent from the detailed description given hereinafter. However,
it should be understood that the detailed description and specific
examples, while indicating a preferred embodiment of the invention,
are given by way of illustration only, since various changes and
modifications within the spirit and scope of the invention will
become apparent to those skilled in the art from this detailed
description.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will become more fully understood from the
detailed description given hereinbelow and the accompanying
drawings which are given by way of illustration only, and thus are
not limitative of the present invention and wherein:
FIG. 1 is a circuit diagram of a hydraulic circuit associated with
a torque converter having control valves;
FIG. 2 is a graph showing a range of engagement of a lockup clutch
as determined according to the relationship between throttle valve
openings and vehicle speeds;
FIG. 3 through 6 and 8 through 11 are flowcharts of sequences for
controlling solenoid valves to control the operation of the lockup
clutch;
FIG. 7 is a graph showing speed ratios of the lockup clutch plotted
against time;
FIG. 12 is a graph illustrating the relationship between duty
ratios of the solenoid valves and the engine torques; and
FIG. 13 is a table of solenoid valve control variables for
respective ranges.
DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 shows a hydraulic circuit associated with a torque converter
5 and having an apparatus for controlling a lockup clutch or direct
coupling mechanism according to the present invention. The torque
converter 5 has a lockup clutch 6 for directly connecting an
impeller 5a and a turbine 5b of the torque converter 5. Operation
of the lockup clutch 6 is controlled by a lockup shift valve 20, a
lockup control valve 30, and a lockup timing valve 40 which are
operated dependent on on/off operation of a first solenoid valve 7
and duty-ratio operation of a second solenoid valve 8.
The lockup clutch 6 is operated according to driving conditions of
an automobile on which the torque converter 5 is mounted, for
increased drivability and fuel economy. The amount of engagement of
the lockup clutch 6 is controlled by the valves 20, 30, 40 so as to
be selectively in a lockup off range, a lockup control range, a
full lockup range (tight condition), and a decelerating lockup
control range. The lockup control range comprises a feedback range,
a control range, a first semitight range, and a second semitight
range, as described later on.
Oil is sucked by an oil pump 2 from an oil sump 1 through an oil
passage 101 into an oil passage 102. The pressure of the oil thus
supplied to the oil passage 102 is then regulated into a line
pressure by a regulator valve 3 connected to the oil passage 102 by
a branch oil passage 103. The line-pressure oil is supplied through
an oil passage 104 to clutches for effecting gear shifts. An oil
passage 105 is branched from the oil passage 104 and connected to a
modulator valve 4 by which the line pressure from the oil passage
105 is regulated into a modulated pressure that is supplied to an
oil passage 106.
When the first and second solenoid valves 7, 8 are turned off or
closed, oil passages 7b, 8b connected to the oil passage 106
through respective orifices 7a, 8a are closed by respective spools
of the solenoid valves 7, 8. The modulated pressure acts in oil
passages 110, 111, 112, 113. Therefore, the modulated pressure is
applied to the opposite ends of the lockup shift valve 20 through
the oil passages 110, 113 and 111, moving a spool 21 of the lockup
shift valve 20 to the right (FIG. 1) under the difference between
the applied pressures and the bias of a spring 22. The modulated
pressure is also applied to the lefthand end of the lockup control
valve 30, moving a spool 31 thereof to the right. The modulated
pressure is further imposed on the opposite ends of the lockup
timing valve 40 through the oil passage 113 and an oil passage 114,
and the oil passage 110 and an oil passage 116, whereupon a spool
41 of the lockup timing valve 40 is moved to the right under the
bias of a spring 42.
At this time, the line pressure supplied from the regulator valve 3
to an oil passage 107 is supplied to an oil passage 108 through a
groove in the spool 21 of the lockup shift valve 20, and then
supplied from the oil passage 108 into a release passage 6a in the
lockup clutch 6. Therefore, a clutch plate 6b connected to the
turbine 5b is released from a case 5d connected to the impeller 5a,
thus turning off or disengaging the lockup clutch 6.
The oil discharged from the torque converter 5 to an oil passage
131 flows through a torque converter relief valve 9 into a cooler
oil passage 132. The oil discharged from the torque converter 5 to
an oil passage 133 flows through a groove in the spool 21 and an
oil passage 134 into the cooler oil passage 132. The oil then flows
from the cooler oil passage 132 through an oil cooler 11 by which
the oil is cooled. The cooled oil returns through an oil passage
135 into the oil sump 1. In order to protect the cooler oil passage
132 and the cooler 11, a cooler relief valve 10 is connected to the
cooler oil passage 132 for releasing excessive oil pressure.
A lockup control mode of operation will be described below. In the
lockup control mode, the amount of engagement of the lockup clutch
6 is controlled dependent on an increase in vehicle speed and
engine output power by turning on or opening the first solenoid
valve 7 and controlling the duty ratio of the second solenoid valve
8. When the first solenoid valve 7 is turned on, the modulated
pressure in the oil passage 110 which has acted on the lefthand end
of the lockup shift valve 20 is released, thus reducing the force
tending to move the spool 21 rightward while it is still moved to
the right. Since the oil passage 110 communicates with the oil
passage 116, no oil pressure acts on the righthand end of the
lockup timing valve 40, which remains moved to the right because it
has already been moved to the right.
When the duty ratio of the second solenoid valve 8 is controlled,
the oil pressure in the oil passages 112, 113 is controlled
according to the controlled duty ratio so as to be lower than the
modulated pressure in the oil passage 106. The
duty-ratio-controlled oil pressure is lowered as the ratio of an
on-duty signal is increased. As the vehicle speed increased, the
ratio of the on-duty signal is increased, and the oil pressure
which has been applied from the oil passage 113 to the lefthand end
of the lockup shift valve 20 decreases, and the spool 21 of the
lockup shift valve 20 is moved to the left by the modulated
pressure acting on the righthand end of the spool 21 from the oil
passages 106, 111. When the spool 21 is moved to the left, the line
pressure supplied from the oil passage 106 is supplied to the oil
passage 133, from which the line pressure is supplied into the
torque converter 5 to increase the internal pressure of the torque
converter 5. The clutch plate 6b of the lockup clutch 6 is
therefore pressed toward the engaging position, i.e., toward a side
of the case 5d, with a back pressure (reaction pressure) developed
in the release passage 6a.
The internal pressure of the torque converter 5 acts in a direction
to engage the clutch plate 6b with the case 5d, and the back
pressure acts in a direction to disengage the clutch plate 6 from
the case 5d. The release passage 6a in which the back pressure is
developed is connected to the lockup control valve 30 through a
groove in the spool 21 of the lockup shift valve 20 and the oil
passage 115. Therefore, the spool 31 of the lockup control valve 30
is pushed to the left under the back pressure from the torque
converter 65. The duty-ratio-controlled oil pressure from the
solenoid valve 8 is applied to the lefthand end of the spool 31
through the oil passage 112. As the ratio of the on-duty signal is
increased, the duty-ratio-controlled oil pressure is lowered, and
hence the force tending to move the spool 31 to the right under the
duty-ratio-controlled oil pressure varies dependent on the duty
ratio of the solenoid valve 8. The lefthand end of the spool 31 is
also subjected to the internal pressure of the torque converter 5
through the oil passages 117, 118, thus the spool 31 being pushed
to the right. Accordingly, the back pressure of the torque
converter 5 and the bias of the spring 32 are applied to the
righthand end of the spool 31, whereas the duty-ratio-controlled
oil pressure and the internal pressure of the torque converter 5
are applied to the lefthand end of the spool 31. The back pressure
of the torque converter 5 varies dependent on the
duty-ratio-controlled oil pressure. By varying the duty-ratio
controlled oil pressure, the back pressure of the torque converter
5 can be controlled to control the amount of engagement of the
lockup clutch 6.
The lockup control mode is effected as described above. When the
ratio of the on-duty signal for the second solenoid valve 8 reaches
100% (i.e., the second solenoid valve 8 is turned on), and then the
first solenoid valve 7 is turned off, a full lockup mode is
effected. When the first solenoid valve 7 is turned off, the
modulated pressure is applied to the righthand end of the lockup
timing valve 40 from the oil passages 110, 116. Since the second
solenoid valve 8 is on at this time, no oil pressure is present in
the oil passages 113, 114, allowing the spool 41 of the timing
valve 40 to move to the left. Therefore, the oil passage 118 is
connected to drain, and the spool 31 of the lockup control valve 30
is held in the leftmost position. The release passage 6a of the
torque converter 5 is connected to drain through the oil passages
108, 115, thus eliminating the back pressure of the torque
converter 5. The lockup clutch 6 is fully engaged.
As described above, the amount of engagement of the lockup clutch 6
can be controlled by turning on and off the first solenoid valve 7
and controlling the duty ratio of the second solenoid valve 8.
Specific driving conditions while the amount of engagement of the
lockup clutch 6 is being controlled will be described below with
reference to the graph of FIG. 2.
The graph of FIG. 2 has a vertical axis representing throttle valve
openings and a horizontal axis representing vehicle speeds. The
figure shows two ranges divided from each other by a lockup-on line
m (indicated by the solid line). The range on the lefthand side of
the lockup-on line m is an off range A. When the driving condition
determined by the throttle valve opening and the vehicle speed is
in the off range A, the lockup clutch 6 is controlled to be turned
off or disengaged. When the driving condition is shifted from the
off range A across the lockup-on line m into a lockup range on the
righthand side of the lockup-on line m, the lockup clutch 6 is
controlled to be engaged. A lockup-off line n is present on a
lower-vehicle-speed side of the lockup-on line m with a certain
range of hysteresis therebetween. After the driving condition has
entered the lockup range, the lockup clutch 6 is turned off when
the driving condition goes across the lockup-off line n entering
the off range A.
The lockup range is divided by five lines a through e indicated by
the dot-and-dash lines in FIG. 2 into five ranges, i.e., a feedback
range B, a control range C, a first semitight range D, a second
semitight range E, and a tight range F. There is also a
decelerating lockup range G in which the throttle valve opening is
substantially zero and the vehicle speed is higher than a
predetermined speed (about 25 km/h).
The amount of engagement of the lockup clutch 6 is controlled
according to the above ranges. The sequence of controlling the
lockup clutch 6 will be described below with reference to the
flowchart of FIG. 3.
First, a step S1 determines a period of time during which the
lockup clutch 6 is to be turned off. More specifically, when a gear
shift is effected manually by operating a shift lever or a
normal/power mode selector switch, the lockup clutch 6 is turned
off for a certain period of time. Then, a step S2 determines
whether the lockup clutch 6 is to be turned off during an automatic
gear shift. When an automatic gear shift is to be effected, it is
detected whether the gear shift is an upshift or downshift, and
also the throttle valve opening is determined. Based on the
detected data, the step S2 determines whether the lockup clutch 6
is to be turned off or not. Thereafter, control goes to a step S3
which determines whether the lockup clutch 6 is to be turned off
because the oil in the torque converter 5 is extremely low or high
in temperature. If the lockup clutch 6 is to be turned off in each
of the above steps, then the lockup clutch 6 is turned off or
disengaged in a step S8.
After the step S3, control proceeds to a step S4 to determine
whether the automobile is being decelerated or not based on how the
vehicle speed or the throttle valve opening varies. If the
automobile is being decelerated, then a step S5 determines whether
a decelerating lockup control mode is to be effected based on the
oil temperature, the vehicle speed, and the engine rotational
speed. If necessary, control goes to the step S8 to turn off the
lockup clutch 6.
If it is determined that the automobile is not being decelerated in
the step S4, then a step S6 determines which range in the map of
FIG. 2 the driving condition is in. The operation of the first and
second solenoid valves 7, 8 is then controlled dependent on the
determined range in a step S7.
Control operation in the step S7 will be described in detail with
reference to FIG. 4.
The control sequence shown in FIG. 4 determines which range the
driving condition is in from a lockup zone code KZ in steps S10
through S30. The lockup zone codes KZ are numerals allotted to the
respective ranges in the decision step S6 shown in FIG. 3. KZ=0 for
the off range A, KZ=1 for the decelerating lockup range G, KZ=2 for
the feedback range B and the control range C, KZ=3 for the first
semitight range D, KZ=4 for the second semitight range E, and KZ=5
for the tight range F. Control goes to the step S6 only when the
driving condition is in the lockup range and KZ=2, 3, 4, or 5.
If KZ=2 in a step S10, then the driving condition is in the
feedback range B or the control range C, and control proceeds to a
step S11. The step S11 determines whether a prescribed period of
time LD2 has elapsed from the time when the driving condition has
shifted from the off range into the range B or C. This is to engage
the lockup clutch with a certain time delay when the driving
condition is shifted from the off range A into the lockup range.
Until the value of a delay timer LDT becomes larger than the delay
time LD2, the control flow goes to the return step.
If LDT.gtoreq.=LD2, then a learned value D.sub.OS (described later
on) is stored as an off duty ratio D.sub.OM in a step S12, and a
feedback component for controlling the duty ratio of the second
solenoid valve 8 is determined in a step S13. The step S13 will be
described later on. In a next step S14, Z.sub.ON control is
effected to lessen an abrupt change in the duty ratio due to a
shift between the ranges to prevent a shock which would otherwise
result from the abrupt change in the duty ratio. Since the first
solenoid valve 7 is required to be turned on for the control in the
feedback range B or the control range C, a command is issued to
turn on the first solenoid valve 7 in a step S15, after which the
control flow goes to the return step.
If KZ=3 in the step S20, the driving condition is in the first
semitight range D, and control goes to a step S21. Until the delay
timer LDT becomes larger than a predetermined delay time LD3 after
the driving condition entered the range D, control does not go to a
step S22. In the step S22, a value produced by subtracting a fixed
value D1 from the latest learned value D.sub.OS is stored as the
off duty ratio D.sub.OM. The learned value D.sub.OS is indicative
of an off duty ratio. By subtracting the fixed value D1 from the
learned value D.sub.OS, the on duty ratio is increased, so that in
the first semitight range, the off duty ratio D.sub.OM is set to a
value for achieving an amount of engagement of the lockup clutch
which is a fixed amount larger than the amount of engagement
thereof based on the learned value D.sub.OS. In order to prevent a
shock from being produced by the abruptly changed duty ratio,
Z.sub.ON control is effected in a step S23 to change the duty ratio
smoothly. In the first semitight range D, it is necessary to turn
on the first solenoid valve 7, and hence a command is issued to
turn on the first solenoid valve 7 in a step S24, after which the
flow goes to the return step.
If KZ=4 in the step S30, the driving condition is in the second
semitight range E, and control goes to a step S31. Until the delay
timer LDT becomes larger than a prescribed delay time LD4 after the
driving condition entered the range E, control does not go to a
step S32. In the step S32, the value of the off duty ratio D.sub.OM
is set to 0. Then, Z.sub.ON control is effected in a step S33, and
a command is issued to turn on the first solenoid valve 7 in a step
S34, after which the flow goes to the return step.
If KZ is not equal to 4 in the step S30, then KZ=5 and the driving
condition is in the tight range (full lockup range) F. Control goes
to a step S40. Until the delay timer LDT becomes larger than a
prescribed delay time LD5 after the driving condition entered the
range F, control does not go to a step S41. In the step S41, the
value of the off duty ratio D.sub.OM is set to 0. Then, Z.sub.ON
control is effected in a step S42.
Control proceeds to a step S43 which determines a Z.sub.ON
execution flag FZ is 1 or not. The Z.sub.ON execution flag is set
to 1 while the duty ratio is being corrected under the Z.sub.ON
control. After the flag FZ becomes 0, i.e., after the duty ratio
correction is finished, control goes to a step S44 in which a
command is issued to turn on the second solenoid valve 8.
Thereafter, a step S45 determines the value of a solenoid on timer
T.sub.Z1 has become 0 or not. Until it has become 0, the first
solenoid valve 7 remains on in a step S46. When the value of the
timer T.sub.Z1 become 0, a command is issued to turn off the first
solenoid valve 7 in a step S47. Stated otherwise, the tight
condition (full lockup condition) is achieved by switching the
first solenoid valve 7 from the turned-on condition to the
turned-off condition. Such switching of the first solenoid valve 7
is effected after having waited for a certain period of time.
The controlling operation in the feedback region B and the control
region C effected in the step S13 will be described in detail with
reference to FIG. 5.
In the control operation, decision steps S51 through S55 are first
executed. A step S51 determines whether a feedback inhibit flag Fep
is set to 1 or not. If it is set to 1, then control goes to a step
S57.
A step S52 determines whether a throttle valve opening TH is larger
than a cruise decision throttle valve opening THCR. The cruise
decision throttle valve opening THCR is the same as the throttle
valve opening indicated by the dot-and-dash line a by which the
feedback range B and the control range C are divided from each
other. The condition TH>THCR means that the driving condition is
in the control range C. In this case, control goes to a step
S57.
The step S53 determines whether the brake is applied or not. If the
brake is in operation, control goes to the step S57.
A step S54 determines whether a temperature range code NT is 2 or
not. If NT=2, then control goes to the step S57. The temperature
range code NT can have one of five values at a time, ranging from 0
to 4 dependent on the temperature of the oil in the torque
converter. The ranges 0 through 4 of the temperature range code NT
indicate a very low temperature, a low temperature, a normal
temperature, a high temperature, and a very high temperature,
respectively. If the temperature is very low or very high (NT=0 and
4), the lockup clutch is off in the step S3 of FIG. 3. Therefore,
the flow of FIG. 5 is executed only when NT=1 through 3. If NT=2
(normal temperature), control goes to a step S55, and if NT=1 or 3
(low or high temperature), control goes to the step S57.
The step S55 determines whether an engine coolant temperature TW is
higher than a feedback control permission temperature DTW or not.
If lower than the feedback control permission temperature DTW, then
control proceeds to the step S57, and if higher than the feedback
control permission temperature DTW, then control goes to a step
S56.
In the step S57, a correction permission flag F.sub.CR is set to 0.
Then, a sampling counter value P is set to 0 and a speed ratio
integral SUM(e) is set to 0 in respective steps S58, S59. As can be
understood from the decision step S52, control proceeds to the step
S57 when the driving condition is in the control range. In this
case, the latest learned value D.sub.OS stored in the step S12
shown in FIG. 4 is used as the off duty ratio D.sub.OM for the
second solenoid valve 8.
Control goes to the step S56 when the driving condition is in the
feedback range. In this case, feedback control according to a C-e
control process is effected. The details of the C-e control process
in the step S56 will be described with reference to FIGS. 6 through
11.
As shown in FIG. 6, the C-e control process comprises an average
speed ratio calculating routine "e.sub.av cal" (step S61) for
calculating the average value of ratios e of the rotational speeds
of the input and output members of the lockup clutch in each
average calculating time period T.sub.CR, an e.sub.av correcting
routine (step S62) for correcting the duty ratio to bring the speed
ratio e into a target speed ratio range (extending from e.sub.L to
e.sub.H and corresponding to a predetermined reference range as
recited in the claims) based on the difference between the
calculated average speed ratio e.sub.av and the target speed ratio
range, an e.sub.H correcting routine (step S63) for correcting the
duty ratio on a real-time basis to bring the speed ratio e back
into the target speed ratio range when the speed-ratio e exceeds
the upper limit e.sub.H of the range for a predetermined period of
time T.sub.eH or more, and a D.sub.OS updating routine (step S64)
for updating, as required, the latest value of the duty ratio
obtained by the above routines and storing the updated duty ratio
value as the learned value D.sub.OS.
Prior to describing the above routines (steps S61 through 64), this
control process will briefly be described with reference to FIG. 7
which shows how the speed ratio e varies according to the control
process.
The graph of FIG. 7 has a vertical axis indicating speed ratios e
and a horizontal axis indicating time. The solid-line curve in the
graph represents how the speed ratio e actually varies. The target
speed ratio range lies between the lower speed ratio limit e.sub.L
(e.g., e.sub.L =0.95) indicated by the dot-and-dash line and the
upper speed ratio limit e.sub.H (e.g., e.sub.H =0.98) indicated by
the dot-and-dash line. In the step S62, the speed ratio e is
controlled so as to be in the target speed ratio range based on the
difference between the average speed ratio e.sub.av (indicated by
thicker lines) calculated in each average calculating time interval
T.sub.CR and the target speed ratio range.
If the actual speed ratio e exceeds the upper speed ratio limit
e.sub.H during the control step S62, the speed ratio e becomes very
close to 1.0 (full lockup condition) and easily becomes 1.0. If the
speed ratio e become 1.0 and the clutch is fully locked up, then
insofar as the driving condition is in the feedback range B, engine
vibrations are transmitted to the driving system and the automobile
body, thereby producing noise. To avoid this, it is desirable to
reliably prevent the lockup clutch from being fully locked up. To
this end, if the speed ratio e exceeds the upper limit e.sub.H for
the predetermined period of time T.sub.eH or more, the above
control routine based on the average speed ratio e.sub.av is not
effected, but the duty ratio is controlled to keep the speed ratio
e in the target range on a real-time basis based on the speed ratio
e at the time (step S63).
The duty ratio corrected based on the average speed ratio e.sub.av
in the above control step is updated each time so that its value
becomes appropriate and stored as the learned value D.sub.OS (step
S64).
The routine of the step S61 is shown in FIG. 8. A step S70 first
determines whether the value of a sampling timer T.sub.SP becomes 0
or not. If it becomes 0, then control goes to a step S71 to
determine whether the value of a sampling counter P becomes a
sampling number a. The sampling timer T.sub.SP indicates a periodic
interval for detecting the speed ratio. The speed ratio is detected
a times at the periodic interval, and the detected speed ratios are
averaged to calculate the average speed ratio e.sub.av. The average
calculating time interval T.sub.CR =T.sub.SP .times.a.
Until the value of the sampling counter P reaches a, control goes
to a step S72 to increment the value of the sampling counter P by 1
at each periodic interval of the sampling timer T.sub.SP, and a
presently detected speed ratio e(P) is added to the previous speed
ratio integral e to find a present speed ratio integral SUM(e) in a
step S73. In this manner, from P=0 to P=(a-1), i.e., during
T.sub.CR, the sum of speed ratios e(P) detected a times, i.e., the
integral SUM(e) of the speed ratios e in the average calculating
time interval T.sub.CR is determined in each average calculating
time interval T.sub.CR.
At a time when P=a, control proceeds from the step S71 to a step
S74 in which the speed ratio integral SUM(e) determined as
described above is divided by the sampling number a to calculate
the average speed ratio e.sub.av in the present average calculating
time interval T.sub.CR. Thereafter, the sampling counter P is set
to 0 in a step S75, and the speed ratio integral SUM(e) is set to 0
in a step S76 in order to calculate the average speed ratio in a
next average calculating time interval T.sub.CR. Then, dependent on
the calculation of the average speed ratio ezv, a correction timing
flag F.sub.ce and a correction permission flag F.sub.CR are set to
1 in steps S77 and S78, respectively.
The e.sub.av correcting routine (step S62) for correcting the duty
ratio by using the average speed ratio e.sub.av thus determined
will be described with reference to the flowchart of FIG. 9.
In this flow, a step S80 determines whether the correction
permission flag F.sub.CR is 1 or not. If it is 0, then a learned
value updating timer TD.sub.OS is set to 0 in a step S81. Then a
step S82 determines whether the correction timing flag F.sub.ce is
1 or not. If it is 0, then the flow of FIG. 9 goes to the return
step.
If the correction timing flag F.sub.ce is 1, then a step S83
determines whether the average speed ratio e.sub.av is greater than
the upper speed ratio limit e.sub.H shown in FIG. 7 or not. If
e.sub.av >e.sub.H, then control proceeds to a step S88. In the
step S88, a less intensive correcting value X.sub.H is determined
by multiplying the difference between average speed ratio e.sub.av
and the upper speed ratio e.sub.H by a predetermined coefficient
Cb. The less intensive correcting value X.sub.H is added to the
previous off duty ratio D used for controlling the operation of the
second solenoid valve 8 to obtain a new off duty ratio D, which is
stored as a controlling duty ratio during the present average
calculating time interval T.sub.CR in a step S89. Thus, the amount
of engagement of the lockup clutch is reduced by an amount
corresponding to the less intensive correcting value X.sub.H,
reducing the speed ratio which has become larger than the upper
speed ratio limit e.sub.H into the target speed ratio range. Then,
the learned value updating timer TD.sub.OS is set to 0 in a step
S90, after which the flow is completed.
If e.sub.av <=e.sub.H in the step S83, then control goes to a
step S84 which determines whether e.sub.av <e.sub.L. If e.sub.av
<e.sub.L, then control goes to a step S85. In the step S85, a
more intensive correcting value X.sub.L is determined by
multiplying the difference between average speed ratio e.sub.av and
the lower speed ratio e.sub.L by a predetermined coefficient Ca.
The more intensive correcting value X.sub.L is substracted from the
previous off duty ratio D used for controlling the operation of the
second solenoid valve 8 to obtain a new off duty ratio D, which is
stored as a controlling duty ratio during the present average
calculating time interval T.sub.CR in a step S86. Thus, the amount
of engagement of the lockup clutch is increased by an amount
corresponding to the more intensive correcting value X.sub.L,
increasing the speed ratio which has become smaller than the lower
speed ratio limit e.sub.L into the target speed ratio range. Then,
the learned value updating timer D.sub.OS is set to 0 in a step
S87, after which the flow is completed.
If e.sub.av >e.sub.L in the step S84, then since the average
speed ratio e.sub.av is in the target speed ratio range, control
goes to a step S91 in which the value of the learned value updating
timer TD.sub.OS is incremented by 1, and then the flow goes to the
return step.
The e.sub.H correcting routine in the step S63 shown in FIG. 6 will
be described with reference to the flowchart of FIG. 10.
First, a step S101 determines whether the correction permission
flag F.sub.CR is 1 or not. If it is 0, then control jumps to a step
S110 in which an e.sub.H correction determining time T.sub.eH is
set to an initial value. If F.sub.CR =1, then a step 102 determines
whether the actual speed ratio e at the time is higher than the
upper speed ratio limit e.sub.H or not. If e<=e.sub.H, then
control jumps to the step S110 in which the e.sub.H correction
determining time T.sub.eH is set to the initial value.
If e>e.sub.H, then a step S103 determines whether the e.sub.H
correction determining time T.sub.eH is zero or over. If it is
over, then it means that the condition e>e.sub.H has continued
for the e.sub.H correction determining time (prescribed time)
T.sub.eH or longer. If so, control steps following a step S104 are
carried out. If the time T.sub.eH is not over, the flow goes to the
return step.
In the step S104, in order to reduce the amount of engagement of
the lockup clutch to lower the speed ratio e below the upper speed
ratio limit e.sub.H, the off duty ratio D for the second solenoid
valve 8 is corrected by adding a prescribed corrective amount
D.sub.H thereto. Thereafter, in steps S105 and S106, the values of
the sampling counter P and the speed ratio integral SOM(e) are set
to 0. Then, the sampling timer T.sub.SP is set in a step S107. The
Z.sub.ON control permission flag FZ is set to 0 in a step S108, and
the upper limit e.sub.H is immediately corrected without carrying
out the Z.sub.ON control. In a step S109, the learned value
updating timer TD.sub.OS is set to 0. Subsequently, the e.sub.H
correction determining time T.sub.eH is set to the initial value in
the step S110, after which the flow is finished.
The D.sub.OS updating routine in the step S64 of FIG. 6 is
illustrated in the flowchart of FIG. 11. First, a step S121
determines whether the Z.sub.ON control permission flag FZ is 1 or
not, and then a step S122 determines whether the value of the
learned value updating timer TD.sub.OS is greater than a updating
determining time DD.sub.OS or not. If the Z.sub.ON control is not
effected, and the speed ratio e is in the target speed ratio range
for the updating determining time DD.sub.OS or more, the off duty
ratio D at this time is stored as the learned value D.sub.OS in a
step S123. Therefore, the off duty ratio D.sub.OM stored in the
step S12 shown in FIG. 4 is the latest learned value D.sub.OS and
is the most appropriate value at the time for maintaining the speed
ratio e in the target speed ratio range.
The duty ratio for the second solenoid valve 8 is determined
according to the aforesaid control process. Since this duty ratio
is controlled so that the speed ratio e will be in the
predetermined reference range, when an engine torque component is
varied, the amount of engagement of the lockup clutch is varied
dependent on the varying engine torque component to bring the speed
ratio e into the reference range. Therefore, the duty ratio which
is determined as described above is of a value containing a
component corresponding to the engine torque. The duty ratio
required to obtain a speed ratio during running on a sloping road
differs from the duty ratio required to obtain the same speed ratio
during running on a flat road.
In view of this, according to the control process of the present
invention, the component corresponding to the engine torque
(referred to as the engine torque component) is removed from the
duty ratio determined as described above, and the amount of
engagement of the lockup clutch is estimated and set based on the
remaining component (referred to as the feedback component).
This will be described in detail with reference to FIG. 12. It is
assumed that a duty ratio is to be set when the automobile is
normally running at 50 km/h, for example. If the engine torque at
this time is 4 kg-m and the learned value of the feedback component
is 20% as seen from FIG. 12, and the feedback component is
50.times.(20/100)=10%. The on duty ratio for the second solenoid
valve 8 is the sum of both components, i.e., 30%. When the driving
condition is in the first semitight range, a value produced by
adding a fixed value to the above learned value is used as the
feedback component.
The control variables for the solenoid valves in the ranges are
summarized in the table of FIG. 13. When the driving condition is
in the off range, the first solenoid valve 7 and the timing valve
40 are turned off, and so is the second solenoid valve 8. That is,
the on duty ratio of the second solenoid valve is 0%. When the
driving condition is in the feedback range, the first solenoid
valve 7 is turned on and the second solenoid valve 8 is controlled
by the duty ratio which is established by the sum of the feedback
component determined based on the feedback control and the engine
torque component determined dependent on the engine torque at the
time. In the control range, the latest learned value stored in the
feedback control serves as the feedback component, and the second
solenoid valve 8 is controlled by the duty ratio established by the
sum of this feedback component and the engine torque component
corresponding to the engine torque. In the first semitight range,
the second solenoid valve 8 is controlled by the duty ratio which
is established by the sum of the feedback component produced by
adding a fixed value to the latest learned value to increase the
amount of engagement of the lockup clutch, and the engine torque
component. In the second semitight range, the first and second
solenoid valves 7, 8 are turned on, and the timing valve 40 is
turned off. In the tight range, the first solenoid valve 7 is
turned off, and the timing valve 40 is turned on.
In the above embodiment, the ratio of the rotational speeds of the
input and output members of the lockup clutch is employed in
determining the duty ratio for controlling the second solenoid
valve 8. However, the difference between the rotational speeds of
the input and output member may be used instead of the speed
ratio.
While the torque converter is illustrated as the hydrodynamic
driving apparatus in the aforesaid embodiment, another hydrodynamic
driving apparatus such as a fluid coupling or the like, for
example, may be employed.
According to the embodiments, as described above, a parameter
(e.g., the ratio of the rotational speeds of the input and output
members) indicative of the amount of slippage between the input and
output members is measured in each prescribed time interval, and
the average of the measured values of the parameter is determined
in each time interval. A control value for the amount of engagement
of the lockup clutch or direct coupling mechanism in a next time
interval is determined based on the difference between the average
value and the predetermined reference range value. Since the
control value for the amount of engagement of the direct coupling
mechanism is kept at a fixed level for the time interval, the
rotational speeds of the input and output members of the torque
converter are prevented from being surged or varied. As feedback
control is effected based on the average of the parameters in the
prescribed time interval, the automobile is prevented from running
in an embarrassing situation in which it would be accelerated while
the engine rotational speed is being lowered.
The control apparatus of the present invention employs, as control
oil pressures, the constant oil pressure supplied dependent on the
turning on and off of the first solenoid valve and the
duty-ratio-controlled oil pressure supplied dependent on the duty
ratio control of the second solenoid valve, for controlling the
operation of the lockup shift valve, the lockup control valve, and
the lockup timing valve to engage and disengage the lockup clutch
and control the amount of engagement of the lockup clutch. The
lockup clutch can be stably controlled without using the throttle
pressure which tends to become unstable as when gear shifts are
effected.
The invention being thus described, it will be obvious that the
same may be varied in many ways. Such variations are not to be
regarded as a departure from the spirit and scope of the invention,
and all such modifications as would be obvious to one skilled in
the art are intended to be included within the scope of the
following claims.
* * * * *